The lateral fins are disposed in the base of the surfboard. The lateral fins are typically formed with plastic foam (polyurethane) molded and covered by a fine layer of polyester resin reinforced with fiber, usually of glass, as has been done since approximately the 1950s. The lateral fins constitute an important accessory of the surfboard, in view of the fact that surfers depend on the positioning of the fins and their disposition in the surfboard to have greater projection and speed or greater stability or greater performance during maneuvers. To meet this need, different fin fitting techniques and positioning techniques have been adopted by others.
In previously developed fin assemblies, the lateral fins are commonly fixed on the lower part of the board, in numbers of one or more, with a current preference of three fins. In previously developed fin assemblies, one of four existing methods are used: (i) fastening the fins to the board through resin reinforced with fiber around the base of the fins, the “adhesive method”; (ii) the use of a “fin box”, that allows, theoretically, the removal in cases of damages limited to the fins; (iii) a movable arrangement that allows the fin to be inserted and removed from a compartment inside of the board; (iv) a movable arrangement that, besides allowing the inserting and removal of the fins, allows the movement of the fin fore and aft within the compartment on the board.
It happens that each one of those methods still does not permit the surfer to adjust the fins to the personal and environmental circumstances of each case. (i) The adhesive method of adhering the fins to the boards with fiberglass involves considerable costs of manual work to get the required smooth finish and requires the performance of difficult and high quality work. The adhesive method also interferes in the hydrodynamic properties of the fins, results in a decrease in the height executes of the fin and causes the fixation area to cause water to be pushed outward from the fixation area, generating turbulences and cavitations. Another great disadvantage in the adhesive method is that if any damage occurs to the fin, the entire board remains disabled. (ii) When a “fin box” is used, the disadvantage is noted in the large fin box used during fixation of the fins to the board. The large fin box is expensive and harmful to the board, for it increases the weight of the board and the less strong fixation of the fins to the board can harm the performance and the safety of the fin assembly during use. The advantage regarding fixation by use of a fin box compared to the adhesive method is that the fin box makes possible the removal of the fins in cases of substitution for repairs or transport. However, this advantage is outweighed by its complex structure making adoption difficult. (iii) With regard to the moveable arrangement installed inside the board that allows the more facilitated removal of the fins, although an improvement, doesn't also satisfy the needs of being able to adjust the position of the fins to the conditions of the sea and skill of the user. (iv) While this technique is the most advanced in the art, i.e., having the moveable arrangement accommodation inside the board, because, besides allowing the removal and insertion of the fin, it possesses a longitudinal fitting to receive a member of fixation of the fin through the end of the bow or stern in relation to the fin. Although providing a notable advantage to surfers by providing increased stability, the technique is still lacking since adjustment of an angle of the fin to reduce drag is not permitted, and it results in cavitations and enlarges the projection of the fin and decreases performance during maneuvers.